Radio transmission system



Jan. 31, 1933. I J, HAMMOND, JR 1,895,459

RADIO TRANSMISSION SYSTEM Filed July 16. 1927 2 Sheets-Sheet l lNVENTOR ATTORNEY JOHN HAYS HAMMGND .m.

Jan. 31, 1933. J HAMMOND, J 1,895,459

RADIO TRANSMISSION SYSTEM Filed July 16, 1927 2 $heetsSheet 2 s??? LE l l l l N 1' I l l l l li 1| llllllM- w INVENTOR 1mm ms MMOND .m.

W22 t/a ATTORNEY Patented Jan. 31, 1933 was JOHN HAYS HAMMOND, JB., OF GLOUCESTER, MASSACHUSETTS t RADIO TRANSMISSION SYSTEM Application filed July 16, 1927. Serial No. 206,331.

The object of this invention is to provide means whereby radio communication may be carried on between two parties without the knowledge of a third disinterested party.

'5 Another object of this invention is to provide a system of radio communication which shall be more free from interferences, from static and other disturbances. V

In accordance with the present invention 1:9. transmission is carried on over a number of radio frequencies, the intensity of each of which may be varied in order to send signals.

This invention relates to the provision of a means for transmitting signals according to the variation of intensity of the total trans mission energy.

In the embodiment shown a plurality of carrier frequencies are employed and the variations in the relative intensity of the ".3 several emitted-wave forms determines the operation of the indicating apparatus. lVhile the system may be employed with as few as two carrier waves, it has been shown in the embodiment with four carrier waves, the intensity of which may be varied by adjusting the several contact switches forming a part of the plate circuit of the respective amplifying tubes. The signals may be transmitted by varying the intensity of each of the carriers by a slight amount which would be insufficient to control an unauthorized receiving station, but suiiicient when combined with the variation of the energy emitted by the other trans? mitters to control the legitimate receiving 1 station.

Thissystem may also be used by varying first the intensity of one carrier and then shifting to the next carrier, etc. so that unauthorized listeners will receive only a chopped up message, but the total energy re ceived by the authorized receiving station will be varied properly regardless of which carrier is having its intensity varied.

Other objects and uses of this invention will become apparent from the following specification taken in connection with the appended claims.

Embodiments of my invention are illus trated in the accompanying drawings in 9 which Fig. 1 is a transmitter, Fig. 2 a receiver embodying my invention, and Fig. 3 shows a method of utilizing the receiver of my invention.

Referring now more particularly to Fig. 1, 11 shows an oscillator of the ordinary well known type including the hot-cathode 12 which is supplied by the battery 13. 'The plate circuit includes the inductance 14 and the battery 15. The grid circuit comprises the grid 16 and the inductance 17, as Well as the potential source '18.

Inductively coupled to the inductance 17 is the inductance 19 which is in turn coupled to the plate circuit by means of the condensers 20 and 21 which are adapted to govern the frequency of the oscillator. Inductively connected to the inductances 17 and His the inductance 22 of an inductive coupling circuit which includes in addition to the inductance 22, the inductances 23 and 24.

Inductively coupled to the inductances 23 and 24 by means of the inductances 27 and 28 respectively are the filters 2'5 and 26 adapt ed to filter from the output of the oscillator 5 11 undesired frequency such as harmonic and residual frequencies.

Inductively coupled to the output inductance 29 of the filter 26 is the inductance 30 of the rid circuit of the amplifier tube 31, having a hot-cathode 34 heated by the filament battery 35, agrid 32 and a plate 45. Included in the grid circuit is the biasing battery 33. The output circuit of the amplifier 31 includes the plate 45, the inductance 41 and the plate potential battery 36, 37, 38, and 39, the potential of whichis adapted to be varied by the contact switch 40. The radio frequency bypass condenser 46 is connected around the source of plate potential. Inductively coupled to the inductance 41 is inductance 42 of the antenna circuit 43, 42 and 44.

Inductively coupled to the output inductance 46 of the filter 25, is the thermionic wave changer 51, the input circuit of which .includes the inductance 47 and the blaslng battery 48. The output circuit of the. thermionic frequency changer 51 includes the inductance 53 and the high potential battery 50, and has in shunt therewith the condenser 54, which is adapted to tune the circuit 54 and 53 to a frequency of 2 n. Inductively coupled to the inductance 53 is the inductance 56 of the amplifier 60. The input circuit of the amplifier 60 includes the grid 58 and the biasing battery 57. The out put of the amplifier 60 includes the plate 61, the inductance 62 and the high potential battery 64, having in series therewith the addit onal cells 65, 66 and 67 which are controlled by the potential switch 68. In shunt with the battery is the condenser 63 for the purpose of by-passing radio frequency current. Inductively coupled to the inductance 62 isthe inductance 69'of the antenna circuit 70, 69, 71. which is adapted to radiate a frequency of 2 n.

Also inductively coupled to the inductance 53 is the inductance of theinput circuit of the thermionic wave changer or frequency doubler 72, the closed oscillating output cir-' cuit 73 of which is tuned'to a frequency of Inductively coupled to the. inductance of the closed oscillatory circuit '73. is the input inductance of the amplifier 74, which is I adapted to supply the antenna circuit 75 with varying intensity signals at a frequency of 4 n. v

Inductively connected to the inductance of the oscillatory circuit 73, is the inductance 76 of the thermionic frequency doubler 77.

the output closed oscillatory circuit 78 of which is adapted to have a frequency of 8 n. Inductively coupled to the last named induct ance is the input inductance of the amplifier 79,which in turn is adapted to supply the antenna circuit 80 with a varying amount of energy at a frequency of 8 n. i

All four output circuits may use a single antenna of suitable characteristics if des red.

Referring now more particularly to Fig. 2 which shows a form of receiver adapted to be used with my type of transmitter. is an oscillator, similar to the oscillator 11, shown in Fi 1. Inductively coupled to the inductive coupling circuit 91 are the filters 92 and 93 which have a function similar to filters 25 and 26 of Fig. 1. I

The output circuit of the filter 92 is adapted to supply the thermionic frequency changer 94, the closed oscillatory output circuit of which is tuned to a frequency'of2 n. Coupled with the output circuit of 94 is asecoud thermionic frequency changer 95 which has in its output circuit a closed oscillatory circuit which is tuned to a frequency of 4 n. In-

" ductively coupled to this latter output circuit is the input of the thermionic frequency doubler 96 the output circuit of which is tuned to a frequency of 8 n. Inductively coupled to the filter 93 and to the output cir cult of thermionic wave changers 94, 95 and 96 are the input circuits of the thermionic amplifiers 100. 99, 98 and 97 respectively.

At 101 is shown a source of audio frequency. of say a thousand cycles, inductively coupled to the filters 102, 103, 104, and which are for the purpose of removing harmonies from the outputs of said audio frequency source. The outputs of the filters 102 to 105 are inductively coupled to the input circuit of the modulators 97 to 100 inclusive and serve to modulate the output of the filter 93 and the thermionic frequency doublers 94, 95, and 96 at a frequency of a thousand cycles. Inductively coupled to the output circuit of the modulators 97 to 100 inclusive are the filters 106 to 109 inclusive which are for the purpose of removing: the carrier frequency and one side band thereby leaving a side band of'n plus or minus.1,000, 2% plus or minus 1.000, 4 92 plus or minus 1,000, and 8 it plus or minus 1.000.

110 and 111', 112 and 113 represent antenna circuits which are adapted to receive the frequency 8 n, 4 a. 2 and a respectively. Inductively coupled to the inductances of the last-mentioned antenna. circuits are the detectors 114. 115. 116 and 117. the input circuits of which are adapted to be heterodynedby the output from the filters 106, 107, 108 and 1.09.

It is to be understood that a single quadruple tuned'antenna may be substituted for the antennae 110 113.

In order to pronerlv combine the four signals from couplings 118 to 121 in the common circuit. it is of course necessary that the sisrnals he of the same frequenc and in phase. The former requirem nt is readily taken care of due to the fact that the transmitted frequencies and the heterodyninc' frequencies are both multiples Thelatter re quirement may be taken care of by the use of V which is shown in this case as a telephone receiver.

It will be further understood that if the oscillator 101 is operated at a radio frequency.

the output ofth-e detector would be a radio frequency. in which case the condensers 122 to 125 respectivel would be ada ted to tune the output late circuit to the radio frequenc of'the oscillator 101 and that then the freouencv in the \VOT'lZfiiTPHl includin the inductan es 118. to 121 inclusive wou d be a radio frequenc which. howeve nlthouo-h not audible. could p rform a us ful wo rin o erating some mechanism, such as a lamp. etc.

I will now briefly describe the operation of my transmission system as follows:

The oscillations produced by the oscillator 16 and supplied to the amplifier 31 are adapt- 5 ed to supply the antenna circuit 43, 4:2 and 44: with oscillations of an intensity which may be varied as previously described by the switch 40. The frequency doubler 51 doubles the frequency received from the primary oscillator 16 and serves to supply the amplifier 60 with a frequency 2 n which latter supplies the antenna circuit 71, 69 and 70, with a frequency 2 a and the amount of plate cur rent will be proportional to the amount of battery potential as regulated by the voltage switch 68. Similarly a frequency of 4 n and 8 n are supplied to the antenna circuits 7 5 and respectively and regulated to various intensities by the switches in the B battery circuit of the two amplifying tubes. The output from one antenna may be regulated during one portion of a word or message and other outputs varied during other portions which would produce a garbled signal unintelligible to a listener on an ordinary receiver tuned to a single frequency.

However, the total amount of energy transmitted by the four antennae, will be such as to produce readily recognizable signals in the proper receiver which has been shown in Fig. 2.

Fig. 2 shows a receiver which utilizes four antennae tuned to the various frequencies being received and contains an oscillator which produces the basic frequency which is the same as the frequency produced by the oscillator 16. By means of the frequency doublers 94, and 96, the detector circuits of the various antennae are supplied with a heterodyning frequency which will produce with the incoming frequencies 8 n, 4 n, 2 n, and n, the same audio or difference frequency which will act with a cumulative efiect on the work circuit.

It will be readily understood that while Fig. 1 shows the use of a plurality of antennae, a single aperiodic antenna may be utilized which will suffice to radiate the various frequencies and t -e frequencies furthest from the natural frequency of the antenna would be adapted to radiate a greater amount of power than those which are close to the fundamental frequency of the antenna.

It will also be understood that the various inductances 118. 119, and 121 of Fig. 2 might be utilized as the supply to operate the electromagnets of a stock ticker type wheel and by energizing certain of the electromagnets. turn the type wheel varying amount to produce the proper typing, as shown in Fig. 3. The electromagnets energized by the various inductances have different displacements so that a large number of different degrees of rotation of the type 65 wheel may be obtained.

It will be readily apparent that while this system is adapted to transmit by using so small a change in the power transmitted on any wave length that a station tuned in on that single wave length would be unable to receive an intelligible signal, it is perfectly possible to transmit on a certain wave length for a short period of time and then switch over to another wave length in varying proportions, always keeping the same amount of energy in the combined antenna circuit when the signal is being sent and always keeping a considerable amount less than that when the signal is not being sent. F or instance, suppose that no signal is being transmitted when each transmitted amplifier has but a single additional cell in the plate circuit, then for a while transmission might be made by increasing the plate circuit supply of the transmitter sending out the frequency of n to four cells and reducing that of the trans mitter of a frequency of 2 a to no additional cells and then for a while having one additional cell used on the n and the 2 a transmitter while the 4: n transmitter has no additional cell. It will thus be seen that a great number of combinations are possible and that it would be impossible for a receiver not equipped and not understanding the proper combination used to receive an intelligible message.

lVhat I claim is:

1. The method of radio transmission which comprises generating a fundamental frequency, amplifying and transmitting said frequency, doubling the fundamental frequency and amplifying and transmitting the doubled frequency. redoubling said fundamental frequency and amplifying and transmitting said quadrupled frequency, selectively altering the amount of energy transmitted at each of said frequencies and thus varying the total amount of transmitted energy at said frequencies to send a single message.

2. The method of radio transmission which comprises transmitting a plurality of frequencies, varying at various combinations the amount of radio transmission, energy of said frequencies to send a message, receiving said plurality of transmitted frequencies, and providing a heterodyning frequency which will produce with each of said received frequencies a third frequency which will.

tend to act cumulatively upon a work circuit. 3. The method of radio transmission which comprises generating a high frequency, am-

plifying and transmitting said frequency, doubling the frequency and amplifying and transmitting said double frequency, varying the amplitude of the transmission on the several frequencies thus produced, receiving each of said transmitted frequencies and supplying a heterodyning frequency.

which will produce with each of said re- 'ceived frequencies a beat frequency of the sameord-er and which will cumulatively act upon a work circuit to producea single r sult.

4. A radio transmission apparatus comprising a generator of high frequency oscillations, means for producing from said oscillations a plurality of series oscillations of different frequencies, means for amplifying the various oscillations thus produced, means for transmitting said oscillations and means for independently varying the amount of energy transmitted at each of said frequencies to send a single message.

5. A radio transmission apparatus comprising an oscillator of high frequency, means for roducin from the oscillations roduced by said oscillator oscillations of multiple frequency, means for amplifying each of the, oscillations thus produced, and means for varying the amount of enemy transmitted by each of said amplifiers and also the total amount of energy transmitted to send. a single message.

.16. A radio transmission apparatus comprising a generator of high frequency oscillations, means for producing from the output of said generator oscillations of double frequency, means for producing from the output of said last mentioned means a frequency of quadrupled frequency, means for producing from the frequency produced by said last mentioned means a frequency of octupled frequency means for transmitting each of the frequencies thus produced and means for varying the amount of transmitted energy at certain of the various frequencies by a small amount thereby varying the total transmission to send a single message.

.7. A radio transmission system comprising a transmitter and a receiver, said transmitter being adapted to generate a plurality of frequencies and vary the amount of transmitted energy at the various frequencies by a small amount thereby varying the total amount of transmission in accordance with a single message, said receiver comprising means to receive the various frequencies transmitted, means for supplying a frequency to heterodyne with each of said received frequencies, and produce thereby a beat of the same order, and means for combining each of the beat frequencies to produce a single result.

8. A radio communication system comprising a transmitter and a receiver, said transmitter comprising means for generating a plurality of radio frequencies the total output of which is modulated in accordance with a single message by varying the amplitude of various combinations of said frequencies and said receiver comprising means for generating a plurality of multiple frequencies corresponding to the frequencies produced by said transmitter, means for producing a frequency to combine with each of the frequenreceiver having a generator for high fre-,

quency oscillation, a vacuum tube arranged to produce from the oscillations produced by said generator a double frequency, a second vacuum tube device arranged to produce from the double frequency produced in saidfirst vacuum tube device'a frequency of quadrupled frequency, a third vacuum tube device arranged to produce from the oscillation produced by said second vacuum tube device a frequency of eight times the fundamental frequency, means for producing a series ofoscillations of audio frequency, means for combining said last mentioned oscillations with each of the frequencies produced by said frequency doublers, means for removing from the output of said modulating means the fundamental frequency and one side band, means for receiving the transmitted signals, and means for combining with said received signals the output of said filtering means and produce therefrom a heterodyne of the same order, and means for utilizing the resulting heterodyne frequency.

10. The steps in a method of signalling which comprise, generating and transmitting a plurality of frequencies and selectively altering the amount of energy transmitted at various onesof said frequencies so as to vary the total amount of transmittedcnergy to send a single message.

11. The method of signalling which com prises, transmitting a plurality of energy waves of different frequencies and promiscuously altering the amount of energy transmitted of the various waves so as to vary the total amount of transmitted energy to send a single message, and intercepting and combining the transmitted energy for producing a single result.

JOHN HAYS HAMMOND, JR. 

